Glucocorticoids potentiate IL-6-induced SP-B expression in H441 cells by enhancing the JAK-STAT signaling pathway

Abstract

The respiratory distress syndrome (RDS) contributes to perinatal morbidity and mortality associated with preterm birth. Surfactant protein B (SP-B) is decreased in RDS. Both maternal antenatal steroid administration and chorioamnionitis reduce the incidence and severity of RDS. An important mediator in chorioamnionitis is IL-6 using the JAK-STAT signaling pathway for signal transduction. We hypothesized that the steroids, betamethasone (BTM) and dexamethasone (DXM), and IL-6 had synergistic effects on SP-B gene expression and STAT3 phosphorylation in H441 cells. DXM and BTM increased SP-B mRNA levels by 16.5 (13.3)-fold and IL-6 alone by 2.3-fold. After 48-h exposure of cells to DXM or BTM, IL-6 caused a significantly greater increase in SP-B mRNA levels (28.1-fold) than IL-6 or glucocorticoids alone. Whereas IL-6 stimulated tyrosine phosphorylation of STAT3 in a time- and dose-dependent way, DXM and BTM had no effect on STAT3 phosphorylation. Both DXM and BTM could potentiate IL-6-induced phosphorylation of STAT3. The synergism of glucocorticoids and IL-6 on SP-B gene expression and the effect of glucocorticoids on IL-6-induced STAT3 phosphorylation could be blocked by a JAK inhibitor. Expression level analysis showed that glucocorticoids increased the expression of the IL-6-binding α-subunit receptor (IL-6R) on mRNA and protein level. Our findings could represent an example of a pulmonary regulation system in which one role of glucocorticoids is to increase the effect of a cytokine by upregulation of its receptor. The described in vitro interaction of IL-6 and glucocorticoids could help explain the clinical observation that prenatal inflammation in preterm babies with antenatal steroid administration can attenuate severity of RDS.

Antenatal betamethasone attenuates intrauterine infection-aggravated hyperoxia-induced lung injury in neonatal rats

“…On the other hand, it is also known that antenatal glucocorticoids upregulate the levels of the IL-6 receptor in lung epithelial cells in chorioamnionitis, leading to a subsequent induction of signal transducer and activator of transcription 3 and surfactant protein B synthesis, which can result in better lung homeostasis during an inflammatory reaction (29).…”

Amplification of steroid-mediated SP-B expression by physiological levels of caffeine

“…Airway epithelial cells NCI-H441 (H441) were purchased from ATCC (LGC Standards, Teddington, UK) and cultured as described (15).…”

“…Primers for PGCiso1, PGCiso2, CtsH, NpsA, and GAPDH mRNA were humPGCiso1fwd 5=-AGTATGGA-CAGTTTCTCGT-3=, humPGCiso1rev 5=-TGAGGATATAGGAG-GAAGGT-3=, humPGCiso2fwd 5=-TCTACCTCAGCAACCTGGTC-3=, humPGCiso2rev 5=-TGAGATTGGAGACAGGTAGGG-3=, humCTSHfwd 5=-CATTTGCCAGCAACTGGAGGAA-3=, humCTSHrev 5=-ATTGGTTCAGTGCCATTTTAAATG-3=, humNAPSAfwd 5=-TACACCACCGATTTGATCCCA-3=, humNAPSArev 5=-CACC-AATAGTCAGCTTGTCCT-3=, hGAPDHfwd 5=-CAAAGTTGT-CATGGATGACC-3=, and hGAPDHrev 5=-CCATGGAGAAGG-CTGGGG-3=, respectively. PCRs were performed on an ABI Prism 7500 Sequence Detection System (TaqMan) as described (15). In case of measurements including SYBR Green, melt curve analyses were performed to verify single PCR products.…”

“…Immunoblotting was performed as described (15). Blots were probed with primary antibodies to SP-B (generous gift of Dr. Jeffrey A. Whitsett, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH), and ␤-actin (926 -42212; LI-COR, Lincoln, NE), followed by staining with corresponding IRDye secondary antibodies (LI-COR) for 1 h at room temperature.…”

IL-6 in non-alcoholic fatty liver disease – good, evil or both?

“…Source of IL-6 may also have an effect and higher levels in portal vein have been shown to contribute to systemic inflammation and liver injury independent of serum IL-6 [12,16]. IL-6 activity is also influenced by other signalling pathways, cytokines and hormones [42][43][44] and this further complicates interpretation of experimental results. In summary the physiological function of IL-6 in metabolic liver disease is still not well understood.…”